Translating polls into policy outcomes

In a report on last May’s Australian election, Nick Evershed of the Guardian translated live election results into support for specific policy outcomes.

We wanted to make an alternate view of election results that moves the results away from the ‘horse race’ and instead emphasises the policy outcomes of the election – that is, what the outcome will actually mean for people in the real world.

I reckoned you could do the same with polls instead of election results. I selected a number of proposals that have been put to a vote in the Dutch Lower House. Using Tom Louwerse’s Peilingwijzer ‘poll of polls’, I tracked developments in the combined virtual vote share of the parties that have voted in favour of those proposals.

The support for individual parties may show considerable fluctuations, but the combined support for policy proposals is relatively stable. This shouldn’t really come as a surprise. Voters may switch quite easily from one party to the other, but not randomly: they tend to stick to a set of parties with broadly similar values. This suggests that voters will often switch between parties that tend to support the same proposals.

Still, some proposals do show growth or decline in their combined virtual vote share. This includes proposals that were supported by either FvD or PVV but not both: FvD has seen considerable growth in the polls, partly at the expense of PVV. Proposals supported by left-wing parties also saw their support grow somewhat, but not if D66 was among the supporting parties.

So what does this all mean? The chart above doesn’t predict which policies will be implemented after the next election (just like the underlying polls aren’t simply a prediction of the next election result). However, it does appear to be a useful tool to make sense of fluctuations in polls.

UPDATE 21 July 2019 - New Peilingwijzer data has been published since; the chart has been updated to include the fresh data. For the conclusions this doesn’t really make much of a difference.

Caveats

One could argue that how parties vote doesn’t always reflect their position, especially when coalition parties have to stick to concessions they have made in the coalition agreement. I dealt with this by using only proposals (with one exception) on which the coalition parties VVD, CDA, D66 and ChristenUnie did not vote unanimously. Apparently, there was no pressure to vote along coalition lines in these cases.

Voters (and respondents in polls) aren’t always aware of the positions of the parties they support. For example, many voters want the government to reduce income differences. They may (wrongly) assume that the party they support also wants to reduce income differences.

As for the chart: an area chart is always a bit problematic, but it would appear to be a defensible choice when you want to show developments in the combined vote share of a number of parties. I guess it could be improved by putting parties that show large variations in the polls on top and the more stable ones to the bottom.